In this paper, a one-stretch calculation method for multi-stage prestressed space grid structure is presented. The prestress value of the i prestressed bar in a certain stage is taken as the unknown, and the prestress criterion equation is established and solved by structural mechanics method. Then we can calculate the control value of each prestressed rod i times in this stage (including the original internal force value of each prestressed rod), the influence value of post-tensioned prestressed stress on the pre-tensioned prestressed stress, and the internal force and node displacement of the struts of the grid structure until the last time of prestressing in this stage. The final internal force control value, internal force and joint displacement of the prestressed bar of the multi-stage prestressed grid structure can be obtained by repeating this analysis and calculation. With this method, the internal force value of the prestressed rod does not need to be adjusted in the process of prestressed tension, and the operation process of prestressed application can be completed at one time. An example is given to illustrate that the calculation results show that the proposed method is correct, reliable and effective.